“Grease” grossed an astounding $188 million in theaters, mostly upon its original 1978 release. In inflation-adjusted terms, that makes it the 27th biggest hit of all time — bigger than “The Avengers” or “The Dark Knight.” Among live-action musicals, it is second only to “The Sound of Music” (or third behind the partially-animated “Mary Poppins,” if you count that as live-action.)

“Grease,” which in its original theatrical incarnation of 1971 was much rougher, was originally set in a high school where gang violence and teen pregnancy were routine. But after “American Graffiti” and “Happy Days” put a more sentimental gloss on 1950s and early-1960s teens, the musical became sweet and tame.

Moreover, the doo-wop songs of the early rock ’n’ roll era sounded so dated by the late 1970s that producer Robert Stigwood brought in Bee Gee Barry Gibb to write the title song and John Farrar to write the pop-rock number “You’re the One That I Want” and the country-pop ballad “Hopelessly Devoted to You.” Some of the songs from the stage musical were more or less forgotten in the movie.

Olivia Newton-John (then considered so hot she was occasionally known as Olivia Neutron-Bomb) seems the ideal choice to play Sandy, but “Partridge Family” star Susan Dey was offered the part first. She turned it down, citing a need to hasten her advance into career oblivion. And John Travolta, still not a name when the movie was being filmed in the summer of 1977 —Saturday Night Fever would make him a sensation that winter — wasn’t the first choice, either. In 1978, leather jackets and the ’50s were synonymous with Henry Winkler, who played Fonzie on TV’s “Happy Days.”

“I didn’t want to be typecast,” Winkler later recalled, according to Cinemablend. “That’s why John Travolta went on to buy his own plane and I just went home.”